Grounded-source transient electromagnetic method (TEM) has many advantages such as deep exploration, flexible arrangement in rough terrain and high working efficiency. Recently it has got much attention and a series of new methods are available, ranging from surface to airborne and borehole method. In this paper, the authors review the research history of long-offset TEM (LOTEM), short-offset TEM (SOTEM), multi-channel TEM(MTEM), grounded-source semi-airborne TEM and grounded-source surface to borehole TEM, and summarize their research status in forward modeling, system design, inversion, imaging and field working. The results show that, as a well-developed grounded-source TEM, LOTEM has accumulated many research achievements. Although some progress has been made, the researches on other grounded-source TEMs are still in a primary stage and still need further improvement. Valuable research results in LOTEM, for example, noise suppression technology, high dimensional inversion and point interpretation, can be introduced to these newly developed electromagnetic methods, which can help provide solutions for high working efficiency and high resolution deep exploration.

The tin-polymetallic mining area of the Yue'e ore district, XiengKhouang Province, Laos, is located in the west of the XiengKhouang Laos-Changshan Vietnam tectonic magmatic belt. Based on the 1:25 000 valley system soil geochemical survey, combined with an analysis of the characteristics of element variation coefficients and concentration coefficients, the correlation of elements, anomaly verification, and gold and other polymetallic ore prospecting potentials, the authors optimized multiple target and prospects areas. The position of the mineralized body was inferred based on geochemical exploration anomalies in key target areas. Through trench verification and drilling engineering verification, good prospecting results were achieved. The area is considered to have copper, tin, lead, zinc, tungsten. It is shown that this method can quickly delineate the prospecting target area and distant scenic area in the thick coverage area and extensive blank research area of Southeast Asian tropical monsoon climate, and can provide an effective basis for the next exploration work.

The Haiyu gold deposit, as a superlarge gold deposit with gold reserves of 470 t and average grade of 4.30×10^-6, is a typical Jiaojia-type gold deposit. The authors carried out the rock geochemical survey by the samples from drillholes, and detected the enrichment of Au, Cu, Pb, Zn, Ag, As, Sb, Cd, Bi, S and Fe₂O₃ and the depletion of Na₂O, Ba and Sr in the ore-hosting tectonic alteration zone. The authors systematically summarized the geochemical marks used for exploration. The enrichment of S and Au, or called the positive S and Au anomalies, is the typical geochemical mark of the source rock. The enrichment of S, Au, Ag and Bi and the depletion of Na₂O and CaO are typical geochemical marks of the tectonic alteration zone. Based on the above elements and their anomalies, the authors constructed the ore-induced anomaly model of the Haiyu gold deposit, which provides a useful reference for the exploration of the peripheral and deep-seated gold deposits. It is proposed that the main gold orebodies of the ore-forming zone of the sea field may be along ZK2403, ZK3008, and ZK3814 boreholes spread in NEE direction.

Influenced by the difficulty of exploration and poor seismic quality, the exploration of oil-gas resources in the southwest of Tarim Basin has not achieved a substantial breakthrough after decades of work. Based on the latest high-precision aeromagnetic data obtained in Southwest Tarim Basin in recent years, this paper discusses the geological problems related to oil-gas accumulation, such as basement structure of basin, distribution and characteristics of depressions, main fault structures and their controlling rules for oil-gas migration and accumulation, local anomalies and favorable local structures of oil-gas as well as their distribution characteristics. The results of the study can provide important reference for the further strategic selection of oil-gas exploration and deep resource evaluation in Southwest Tarim Basin.

In order to find out the stratigraphic structure and groundwater pollution in the ore concentration area of Guyang County, Baotou City, it is necessary to carry out hydrogeological drilling around typical mines in the ore concentration area. In this paper, according to different types of groundwater-finding targets and the advantages of different measuring devices in resolution and signal-to-noise ratio, the multielectrode resistivity method was employed to study and analyze the electrical structure characteristics and well forming pattern of groundwater around south concentrator of Wengeqi iron deposit, Hongchang concentrator and Shangshierfenzi gold deposit. The result shows that comprehensive analysis of the hydrogeological conditions of the study area and utilization of different arrays of multielectrode resistivity method seem to be effective technical means for carrying out water resources investigation, which can achieve the target, reduce the multi-solution of geophysical inversion and interpretation, greatly improve the efficiency of searching for groundwater resources by using single geophysical method and provide a technical basis for water exploration and well determination in the ore concentration area of Guyang County, Baotou City.

The eastern region of Sichuan basin is located between Huaying Mountain and Qiyaodan Mountain. After multiple periods of complex structural superposition and transformation, high and steep tectonic belts and faults were formed. It is difficult to detect and distinguish hidden faults in the high and steep tectonic belts in geophysical exploration. Based on the forward and inverse simulation results of gravity, magnetic and electric detection methods, the authors have reached the conclusion that buried faults in high and steep fault folds can be detected and recognized. Combined with the practical application effect of gravity, magnetic and electric integrated geophysical prospecting methods in high and steep fault folds in eastern Sichuan, the authors summarized the abnormal morphology and abnormal characteristics of buried faults . At the same time, the experimental results of field data acquisition interference suppression and the forward inversion processing method of fault fracture zone anomalies were also summarized. The results obtained by the authors provide a reference basis and experience accumulation for geological exploration in eastern Sichuan.

With Xiangshan South-Dadiantang area of the Ningwu volcanic basin as an example, the authors used the methods of geology and unmanned helicopter aeromagnetic to explore the prospecting work in the deep and peripheral parts of the old mine. Comprehensive analysis and fine inversion of aeromagnetic anomalies were conducted to determine the location of the borehole. All the drill holes intersected ores in the depth of the old mine, which proves the effectiveness of this method. The result also provides a reference for the rapid and effective development of prospecting work in the deep and peripheral areas of old mines in areas with similar working conditions in the future.

As oil shale is an important unconventional oil and gas resource,its exploration and development has received increasing attention.Microtremor exploration based on seismic ambient noise is a passive,efficient and low-cost method of seismic exploration,which can be used to image the shear wave velocity of underground medium and can become a potential new exploration method for oil shale more in line with the requirements of "environmental protection".For the first time,the authors applied microtremor method to oil shale exploration based on the spatial cross correlations of common central panel and conducted a study of the identification of oil shale in Songliao Basin.The results show that the geometry of microtremor method can be flexible according to the real situation,the shear wave velocity profile corresponds well with the results of borehole cataloging near the survey line and the main stratum is well divided.The second member of the Nenjiang Formation,which is mainly oil-bearing shale,exhibits low velocity characteristics.

Wuerxun Sag is an important oil-bearing area in the south of Hailaer basin, which has great exploration potential. This paper determines the main source rocks in Wuerxun Sag by oil source correlation, analyzes the development characteristics of source rocks in different regions and geochemical indicators such as organic matter abundance and type, evaluates the oil generation maturity and accumulation stage of main source rocks in Wuerxun Sag, and judges the oil and gas filling history and predicts the preferred exploration potential position by measuring the homogenization temperature of fluid inclusions. It is found that the oil source in different areas of Wuerxun Sag is not identical. The oil reservoir in the north of Wuerxun Sag is derived from the parent material of mud shale rock of Nantun formation. In the south of Wuerxun Sag, besides the mud shale of Nantun formation, there is oil flow from dark mudstone of Tongbomiao formation. Wuerxun Sag has two stages of hydrocarbon accumulation: The first stage is from the later Yimin formation to the early Qingyuangang formation; The second stage is the late structural activity of Qingyuangang formation, which makes the early oil reservoir redistribute and inject new traps. It is considered that the west side of Wubei sag and the east side of Wunan sag are two important exploration potential zones.

As one of the important regional faults in northern Ningxia, the Yellow River fault has controlled the formation and evolution of Yinchuan Basin. This fault is one of the inevitable key points for studying the law of seismic activity and geothermal resource enrichment in Yinchuan plain. At present, the study of the Yellow River fault is very insufficient, and the work is mainly concentrated on surface survey with shallow geophysical exploration in some areas. In this paper, the authors used geological outcrop data as clues and, based on regional 1:200000 gravity data, used advanced geophysical data processing techniques such as wavelet demarcation and oblique derivative to clearly depict the phenomenon that the Yellow River fault has obvious characteristics of "flying geese" plane distribution. The fault is divided into four sub-segments: Lingwu section, Linhe section, Yueyahu section and Lihe section. The CSAMT data of Linhe section and Lingwu section reveal that the main fault and its secondary faults of the Yellow River descend gradually from east to west, i.e., "staircase", with obvious "grading" characteristics. The undercut depth of the Yellow River main fault reaches the upper crust, and the combination of the secondary-scale faults on the profile exhibits a typical "broom" shape. The "seat-like" space of "upward steep, moderately gentle, and downward steep" of each fault is obviously present. Compared with the existing research results, it is found that there are three differences between them, i.e., spreading characteristics, spreading position, and spreading relationship.

Danghe Nanshan is one of the important gold metallogenic areas in Gansu Province. A number of important gold deposits have been discovered there, such as Jiagongtai, Heicigou and Langchagou, suggesting that the metallogenic conditions are very favorable. However, due to the special geochemical landscape of this area, the peripheral prospecting effect is not good. When carrying out the 1:50 000 mineral prospect survey project in Heidaban-Danghe Nanshan area and aiming at the low and gentle anomalies in the area, the authors introduced the 1:10 000 tectono-geochemical debris survey method into the gold prospecting work for the first time, and analyzed the geochemical characteristics and element combination characteristics in this area. Combined with the metallogenic geological background, 13 comprehensive geochemical anomalies were delineated, and it was found that the main metallogenic elements Au, Pb and Pb and exploration elements As and Sb are intensively enriched in favorable structural positions. Through trenching, 6 new gold mineralization zones were discovered and 15 gold orebodies were delineated. This method was further applied to the gold prospecting in adjacent areas, with good prospecting results achieved. The successful application of this method is of great significance for prospecting in the geochemical landscape area of shallow covered Alpine desert.

As it is difficult to collect the weathering stream sediments of bedrock in the loess overburden area,the effect of regional geochemical exploration is often not ideal; therefore, regional geochemical exploration work has not been carried out in many loess overburden areasof China. In this paper, the deep-penetrating geochemistry method was used to carry out the experimental study of geochemical prospecting techniques for concealed deposits in the loess overburden area in the Zhonghedi silver-lead-zinc polymetallic deposit in Xiaoshan, Henan Province. The results of fine-grained soil prospecting method and metal mobile extraction measurement show that both methods can well indicate the anomalies of underlying polymetallic orebodies in the loess overburden area and, at the same time, the mobile extraction method further enhances the abnormal indication of ore-forming elements to the orebody, so both methods can be used as effective means in search for concealed polymetallic deposits in the loess overburden area.

There are many Yanshanian granite intrusions in eastern Hebei, which constitute a good metallogenic background of granite-type rare metal deposits. In order to study the metallogenic prospects of these rock masses, the authors chose the Hanerzhuang granitic body in this area as the research object, and carried out the multi-channel energy spectrum survey to analyze the characteristics of radioactive parameters of different lithologies, the characteristics of radioactive anomalies and their relationship with rare metal mineralization. The results show that the average content of U, Th and total trace in the monzogranite is 9 times, 8.5 times and 3.9 times the background value in the whole area, respectively. The distribution characteristics of the anomaly field are basically consistent with the surface outburst form of the monzogranite. Combined with the results of petrogeochemical study and artificial heavy sand, the authors hold that the monzogranite whole rock has a good mineralization of rare metals. The rocks contain a large number of U, Th and Hf minerals such as yttrium-brown niobium ore and monazite, and these minerals have a symbiotic relationship with Nb, Ta, Rb and other rare metal minerals. According to the distribution of anomaly field and the characteristics of thorium potassium, thorium uranium, uranium potassium ratio and other parameters, the favorable areas of rare metal mineralization can be directly delineated to guide the arrangement of prospecting engineering. The effective implementation of this method provides a convenient, efficient and cheap means for the exploration of rare metals in the granite area in the future.

Surface wave dispersion curve inversion is an important geophysical method for obtaining the velocity and thickness distribution of underground shear wave.Conventional linear inversion methods,such as iterative least squares,relying on the initial model and multiple solution,are easy to fall into local minimum and low inversion accuracy.The stochastic inversion method based on Bayesian theory is a nonlinear inversion method which can integrate prior information.This method does not need initial model,only uses prior information to sample the model randomly,and selects and accepts the appropriate inversion model according to the probability distribution.It achieves the accurate estimation of the detail information.In this paper,the authors present a Bayesian Markov Monte Carlo (MCMC) stochastic inversion method based on GPR data constraints to invert the Rayleigh-waves dispersion curve.In the inversion process,by randomly changing the model parameters and calculating the likelihood function of the dispersion curve and the actual dispersion curve,researchers can choose whether to accept the new model parameters,repeat this process continuously,and finally get the best fitting result with the actual dispersion curve and the posterior probability density distribution of the VS solution.The typical numerical model test and field seismic data demonstrate that,compared with the conventional unconstrained stochastic inversion,the proposed method can effectively reduce the multiple solution and improve the efficiency and accuracy.

The target field is in the early stage of development with few drilling wells.Unclear boundary of gas reservoir in the target area affects accurate calculation of oil field reserves and well pattern deployment for later development.To solve this problem,the authors analyzed the seismic response characteristics of gas-bearing reservoirs in the target area by spectral decomposition energy attenuation,AVO analysis and pre-stack elastic parameter inversion technology,and then predicted the boundary of gas-bearing reservoirs in the target area.The result shows that the gas-bearing reservoir in the target area is characterized by "low frequency resonant and high frequency attenuated".That means the increase of low frequency energy and the decrease of high frequency energy due to the attenuation of seismic wave.Through AVO forward analysis of drilled well,it can be determined that the gas-bearing reservoir in the target area belongs to class III AVO anomaly,and its seismic positive amplitude increases with the increase of offset distance.Among the petrophysical parameters,Lame's coefficient,Poisson's ratio and P-S wave velocity ratio are sensitive to gas-bearing sandstone.Besides,Poisson's ratio is the best one for distinguishing gas-bearing sandstone and can reveal the gas-bearing reservoir and predict its plane distribution.Applying spectral decomposition energy attenuation,AVO analysis and pre-stack elastic parameter inversion technology,the authors detected gas-bearing reservoirs. With the application of multi-technology,the prediction precision of gas-bearing reservoir boundary can be improved and this would provide support for accurate calculation of reserves and development of well pattern deployment in the target area.

Seismic wave forward modeling technology is widely used in shallow exploration.This method can combine geological model and seismic model organically to verify and guide the acquisition,processing and interpretation of seismic data.The deep reflection seismic profile detection technology based on the oil reflection seismic technology has been very mature after decades of development and application.But up to now,the application of seismic wave forward modeling in deep reflection seismic profile is very insufficient.In this paper,the deep reflection seismic profile across Sichuan Basin was used to carry out forward modeling.By comparing and fitting the horizon of forward simulation data and actual seismic data,the parameters such as velocity and horizon were constantly modified,and the final depth domain geological model was established,which provides more accurate stratigraphic information such as crustal thickness and Moho depth for structural profile.Through the geological model in depth domain,it is revealed that the angle of Neoproterozoic paleosubduction in the northwest margin of Yangtze plate was about 30 °,and the depth of subduction reached 60 km.

Seismic imaging of the high-steep structural zone in southern Biyang Depression is difficult.In order to improve imaging accuracy,in this paper,the authors studied and applied tomographic static correction technology of undulating surface in the piedmont zone,employed prestack multi-domain noise suppression technology based on low-frequency fault surface waves protection,velocity modeling technology of high-steep structure in the piedmont zone and reverse-time migration technology of undulating surface,and thus improved the seismic imaging accuracy of complex structures in the high-steep structure zone in this area.As a result,large boundary fault zone characterization is more accurate,and the stratigraphic contact relation and structure imaging are clear.

In order to improve the accuracy of prediction of reservoir parameters,the paper proposes the approach for reservoir parameters forecasting based on KICA and Support vector machine (SVM).The KICA attribute optimization technology reflects the non-linear relationship and high order statistical properties of the attributes,extract the reservoir information of mutual statistical independence which reflects the reservoir parameters of the subsurface.SVM technology based on structural risk minimization principle,which can solve problems of the nonlinear systems for the small sample,high dimensional and local minimum.KICA combined the SVM,which accurately predict the reservoir parameter distributions through the huge attribute space and less well data.Through the model and actual data, it shows that reservoir parameter prediction technology has good effect of application, and high prediction.

With the continuous improvement of exploration degree,more and more attention has been paid to low-range structural oil and gas reservoirs.Current methods for identifying low-amplitude structures cannot effectively eliminate low-frequency structural background information contained in seismic data,and cannot accurately identify low-amplitude structures.In this paper,on the basis of de-frequency reduction,the trend decomposition method was used in the search for structural inflection points,and the low-amplitude structure was graphed. Combined with the wavelet decomposition method,the continuity in the large-scale time-frequency domain is good.The inverse transform finally obtains a low-amplitude structure explanatory diagram that eliminates the low-frequency background of the structure.The practical application in the northern part of E Basin shows that the low-amplitude structure identification method based on de-frequency reduction enhances the local micro-structural characteristics,and also makes up for the influence of structural elevation difference and random factors on low-amplitude structures.The purpose of the complete and detailed map is of great guiding significance for the exploration and development of complex oil and gas reservoirs with low structural amplitude.

The vibrator has been widely used in petroleum,coal field and other seismic exploration,and the corresponding technical means are relatively mature;nevertheless,there is no reference basis for the parameter selection of middle and shallow seismic exploration with vibrator.In order to study how to obtain high quality data in middle and shallow seismic exploration,the authors carried out a series of "vibrator excitation,high frequency geophone reception" experiments in Xiong'an.Based on a large number of experimental data and using qualitative analysis of original single shot and quantitative analysis of frequency spectrum,this paper systematically discusses the influence of the selection of parameters such as vibration number of vibrator,sweep length,starting frequency,ending frequency,drive level,slope length and natural frequency of geophone on data quality.This paper clarifies the key points and basis of parameter selection,puts forward the concept of high cutoff frequency,and summarizes the strategy of parameter selection for middle and shallow seismic exploration,which provides some reference for the use of vibrator in middle and shallow seismic exploration.

The traditional seismic P-wave impedance inversion method has the problems of low lithologic resolution and multi-solution,and it is hence difficult for the inversion results to meet the requirements of finely characterizing the lithologic distribution.In this paper,by constructing a normalized pseudo-gamma curve containing lithology and P-wave impedance information as a lithology index indicator curve,the neural network method is used to convert seismic data into a gamma data volume which is more closely related to lithology.Through the neural network seismic inversion,the sand and mudstone lithologic inversion data volume is obtained.This method was used to invert the sand and mudstone lithology of the Pinghu Formation in the Xihu Sag.Compared with traditional methods,the prediction accuracy of the mudstone thickness is up to 93%,which more accurately characterizes the distribution of underground sand and mudstone,and provides a basis for later oil and gas exploration.

Tipper is very sensitive to the lateral inhomogeneity of the geoelectric structure and can be used to characterize the complex structure. In this paper, based on the three-dimensional complex anomalous body model of magnetotelluric sounding, the formula for calculating the three-dimensional tipper is derived according to the definition of the dump, and three-dimensional anomalous volume models with different combinations are constructed for forward modeling. Forward modeling studies show that the tipper data better reflect the abnormal body boundary, and it is also more accurate to reflect the boundary of several abnormal bodies, whereas the low resistivity body sensitively reflects a high resistance abnormal body. The study of tipper data further explains the characteristics and laws of tipper data and provides a theoretical basis for the application of tipper data.

Aiming at tackling the current shortcomings of wide field electromagnetic method data processing software such as low integration, cumbersome operation and inability to manage data in a unified manner, the authors developed wide field electromagnetic method data processing and interpretation software. The software adopts client-server architecture and modular design. The project management module developed based on MySQL database can realize the automatic storage and management of project data. The data processing module of wide field electromagnetic method developed by the scientific computing library based on Python can meet the data processing requirements. Based on visualization and interactive operation, this software can greatly simplify the operation process and improve the efficiency of data processing. This software was applied to actual projects and, as a result, large quantities of data were processed, and good results were achieved.

The forward modeling is an effective way to study the characteristics of transient electromagnetic (TEM) responses. The high precision and fast 3D forward modeling technology is a hot spot in the study of TEM forward modeling. The multiphysics module in ANSYS software is suitable for the forward modeling of TEM. In this paper, the application method of ANSYS software in TEM 3D forward modeling is introduced by some model examples, including the preprocessing, loading, solution setting and post-processing. The numerical results show that the simulation of TEM forward modeling by using ANSYS software has high accuracy. The TEM forward modeling using ANSYS can improve the efficiency of forward simulation calculation and provide a strong support for analyzing and understanding the characteristics of TEM response.

The quality monitoring and evaluation of oil and gas geochemical analysis and testing are not detailed enough in the current standards and specifications, and there are also some differences in quality requirements. Based on a comparison of related contents of the effective national standards, industry standards and enterprise standards and combined with many years of experience in quality management, this paper systematically analyzes and evaluates the monitoring and evaluation methods commonly used in oil and gas geochemical analysis and testing.At the same time,based on the comparative study of the allowable error and the qualified rate of each standard, it is pointed out that the other standards are lower than the national standards in quality and need to be revised in time. This paper also calls for speeding up the development of standard samples for oil and gas geochemical exploration, ensuring the accurate tracing of quantitative values, and promoting and improving the quality monitoring level of oil and gas geochemical analysis and testing.

The traditional transient electromagnetic inversion method using artificial neural network based on gradient descent method is inefficient and can not guarantee global convergence. In order to solve these problems, this paper proposes a transient electromagnetic inversion method based on on online sequential extreme learning machine (OSELM). This approaches is used for inversion of high-dimensional exploration data obtained by transient electromagnetic method. Firstly, the hidden layer parameters (input weight and deviation) are randomly set to simplify the learning process of the model. Then, the prediction samples obtained from the test are added to the training samples as the next update information, and the online sequential extreme learning machine prediction model is established to maximize the inverse accuracy. Finally, the inversion results of two classical TEM layered geoelectric models and a quasi two-dimensional geoelectric model show that the proposed method can solve the problem of nonlinear modeling and high-dimensional data for TEM inversion, and a comparison with extreme learning machine (ELM) shows that this method has more accurate inversion, better generalization ability and higher calculation efficiency, which provides a new idea for the application of neural network in geophysical inversion.

After the formation of water-filled goaf in coal mines, the distribution patterns and locations are different and unclear. Therefore, it can easily cause serious water hazards. In order to accurately locate the water-filled goaf and study its electromagnetic response characteristics, the authors chose the Datong Majiliang coal mine as the engineering background, used acrylic glass shelves as the experimental platform, and took similar simulation materials as each rock layer to design the physical experiment of transient electromagnetic detection in the water-filled goaf under different water accumulation and existence situations of collapsed rock masses. The results demonstrate that, when the goaf is filled with water, the induced electromotive force curve will be affected by the low resistance effect during the attenuation process and produce an abnormal "upward" phenomenon, and the greater the water filling, the more obvious the abnormal amplitude is. The existence of collapsed rock mass will limitedly weaken the abnormal interference of low resistance. When the goaf is not filled with water, the induced electromotive force curve decays normally, and the impact of the collapsed rock mass is negligible.

Huahai basin is in the western edge of the corridor basin group in Gansu Province. Based on the results of soil gas radon concentration measurement and the background structural and evolution law of Huahai basin, the authors analyzed the characteristics of the abnormal fields by the Information Entropy Subinterval Area Median Contrast Filtering (SAMCF) Method. The results were different with the different m and n paraments by using SAMCF method. It also showed that the entropy varied from 2.5 to 3.6. The relationship of entropy and m and n was complexity. However, it varied like a "U" sharp with the incease of k parament. When the k varied from 15 to 20, the minimum entropy was gotten showing the western party of the study area with anomaly radon gas in the soil, is the favorable area for deep uranium exploration.

Kriging interpolation algorithm is the basis of 3D modeling of coal seam occurrence form in fully mechanized mining face based on traditional geostatistics. However, the variation function model selected and fitted by Kriging interpolation algorithm cannot reflect the actual geological characteristics and the variation trend of spatial data. In this paper, UPSO-Kriging interpolation method is thus proposed: PSO algorithm is optimized to solve the problems of slow convergence and easily falling into local solution, and the optimized algorithm UPSO is then introduced into Kriging interpolation to solve the variation parameters and fit the variation function model, thus realizing the height prediction of each layer in the coal seam structure of working face. In addition, with DEM model established on regular grid method, the three-dimensional visualization of the occurrence form of coal seam in fully mechanized mining face is realized by using Three.js, which provides scientific basis for transparent mining, intelligent mining and quality mining of coal enterprises.

The existing geological data show that there are several buried faults in the main urban area of Chengdu. However, the specific location and distribution of these faults are still unclear, which poses great security risks to the comprehensive and scientific exploitation and utilization of underground space resources and the optimization of urban construction planning and layout in Chengdu. In view of such a situation, four geophysical methods, namely, micromotion survey, high-density electrical method, transient electromagnetic method and soil radon measurement, were used in this paper to comprehensively explore the buried Baojiangqiao fault in the work area. The integrated geophysical prospecting methods not only identified the stratigraphic structure along the survey line, but also obtained the location, property, attitude and scale of the buried Baojiangqiao fault. This work indicates that the integrated geophysical prospecting methods can achieve better results in the exploration of urban buried fault.

In an open-pit coal mine in Hulun Buir of Inner Mongolia, the main mining coal seams are buried in depths ranging from 39m to 90m. Before coal mine integration, predatory mining has left many mined areas with unknown geological data, and the existence of mined-out areas has brought huge safety hazards to open-pit mining stripping. In order to find out the specific location and connectivity of the underground goaf, the authors used the cross-hole electromagnetic wave CT method to probe into the inside of the goaf in detail, and obtained a lot of real and reliable geophysical data. The analytical result shows that relatively complete rock formation electromagnetic wave absorption coefficient is in the range of 0.44~0.51Nper/m, and no water-filled goaf electromagnetic wave absorption coefficient is in the range of 0.29~0.40 Nper/m. According to the difference of electromagnetic wave absorption coefficient between goaf and surrounding rocks, the authors drew the morphological interpretation map of the goaf, and the results are basically consistent with the drilling data.